Merge Preprocessed Geospatial Data from CISGO with data_frame from Eurostat

Merges data_frame obtained from Eurostat with get_eurostat with geospatial data preprocessed either using ggplot2::fortify into a data_frame or a regular SpatialPolygonDataFrame. The resulting data_frame can be plotted using ggplot2 and SpatialPolygonDataFrame using sp::spplot.